Silicon is an extraordinarily useful semiconductor, employed in integrated circuits, solar cells and photodetectors; however, it exhibits no significant luminescence at room temperature because of its indirect band gap. Silicon nanocrystals (SiNCs) in the quantum size range (2-12 nm) can be efficient light emitters, with emission wavelength that can be tuned by size from the near-infrared (NIR) into the visible range (McVey, et al. Acc. Chem. Res. 2014, 47:3045-3051; Mastronardi, et al. Adv. Mater. 2012, 24:5890-5898). Moreover, silicon nanocrystals, being composed of a single, elementally nontoxic material that is potentially biodegradable, earth abundant, ecologically safe, and known to be metabolized, may satisfy the above criteria for nanocrystals rapid progression to the clinic. The indirect band gap of silicon, however, still makes light absorption relatively weak compared to nanocrystals of direct band gap semiconductors, especially at wavelengths near the absorption edge. This leads to a large apparent Stokes shift between excitation and emission wavelengths of nanocrystals.
Ding, et al. (J. Science, 2002, 296:1293-1297) discloses induced silicon nanocrystal luminescence by electrochemical charge injection. Liu, et al. (J. Phys. Chem. C, 2008, 112:15865-15869) discloses energy transfer between a perylene diimide derivative and silicon nanocrystals embedded in polymer (PMMA). Rosso-Vasic, et al. (J. Phys. Chem. C, 2009, 113:2235-2240) discloses energy transfer between a Ru-based dye and blue-emitting silicon nanocrystal. Sommer, et al. (J. Phys. Chem. C, 2011, 115:22781-22788) discloses fast energy transfer (270 fs to 3 ns) from vinylpyridine ligands to silicon nanocrystals. Erogbogbo, et al. (Nanoscale, 2012, 4: 5163-5168) discloses enhancement in brightness of silicon nanocrystals by an anthracene-based dye in the hydrophobic core of micelles due to energy transfer.
There is still a need to enhance the optical absorption of nanocrystals. There is still a need to enhance the optical absorption of silicon nanocrystals while retaining their emissive properties. There is still a need to create significantly brighter silicon nanocrystals. In accordance, the present disclosure addresses these needs.